The invention relates to a system for scanning information carriers in cassettes; and more particularly, for recording and/or reading signals on/from information carriers in cassettes, comprising cassettes of a first type and cassettes of a second type, said two types of cassettes being substantially identical in dimensions and shape apart from local distinctive features of a first type and a second type respectively, which system further comprises drive apparatuses constructed for cooperation with a cassette after insertion of a cassette in a correct orientation.
A system of the general type defined in the foregoing paragraph is known as the Compact Cassette system for recording and/or reproducing audio signals on/from magnetic tapes accommodated in cassettes. The system comprises cassettes containing different types of magnetic tape. A first type of cassette belonging to this system contains magnetic tape provided with a magnetic layer on an iron-oxide base. A second type of cassette contains chromium-dioxide magnetic tape. The two types of magnetic tape have different magnetic properties, as a result of which the drive apparatus should be adapted to the specific type of magnetic tape in use. The adaptation mainly affects the magnetic head and, more in particular, the setting of the bias current through the coil of the magnetic head. The drive apparatus may comprise an automatic device for adapting the bias current. Both types of cassettes have distinctive features to distinguish between the magnetic tapes used in the two types. The distinctive feature in cassettes containing chromium-dioxide tape is constituted by a cut-out in the rear wall of the cassette. Cassettes containing iron-oxide tapes can differ in that they do not have such a cut-out. A drive apparatus which is suitable for cooperation with each of the two types of magnetic tape may include a scanner for detecting the presence or absence of the cut-out in the rear wall of the cassette and automatically selecting the correct bias current.
Another known system of the above general type is the V2000 video-recorder system. This system employs three types of cassettes containing different lengths of magnetic tape. A pattern of apertures in the main walls of the cassettes (see United States Patent Specification U.S. Pat. No. 4,339,776, herewith incorporated by reference) can be detected by a drive apparatus by scanning the apertures to determine the length of the magnetic tape contained in the cassette being used.
In the aforementioned prior-art systems the cassettes can be distinguished from one another in that specific apertures in the cassette housing are present or absent. For the remainder, the cassettes are substantially identical to one another at least as regards their external dimensions and shape and therefore they can be loaded into any drive apparatus belonging to the system. However, there may be systems in which this is undesirable.